Transparent substrate provided with a stack of thin layers, application to thermal insulation and/or solar control glazings

ABSTRACT

The invention relates to a transparent substrate, more particularly of glass and having multiple thin layers on which are successively deposited;  
     i) a first dielectric material layer,  
     ii) a first layer having infrared reflection properties, particularly based on metal,  
     iii) a second dielectric material layer,  
     iv) a second layer having infrared reflection properties, particularly based on metal,  
     v) a third dielectric material year,  
     characterized in that the thickness of the first layer having infrared reflection properties corresponding to about 50 to 80%, particularly 55 to 75% and preferably 60 to 70% of that of the second layer having infrared reflection properties.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to transparent and in particular glasssubstrates covered with a stack of thin layers incorporating at leastone metal layer able reflect solar radiation and/or infrared radiationof considerable wavelength.

[0003] The invention also relates to the use of such substrates for themanufacture of solar protection or control and/or thermal insulationglazings. These glazings are used both for equipping buildings andvehicles, with a particular aim of reducing air conditioningrequirements and/or reducing excessive overheating resulting from theever-increasing size of the glazed surfaces in car bodies.

[0004] 2. Discussion of the Background

[0005] A known layer stack type for giving solar protective propertiesto substrates is constituted by at least one metal layer, such as asilver layer, which is placed between two dielectric material layers ofthe metal oxide type. This stack is generally obtained by a successionof deposits carried out by a method using a vacuum such as magneticfield-assisted cathodic sputtering.

[0006] Thus, patent application WO 90/02653 discloses a laminatedglazing intended for cars and whose outermost glass substrate withrespect to the vehicle body is provided with a stack of five layers onits inner face in contact with the thermoplastic material interlayer.This stack consists of two silver layers intercalated with three zincoxide layers, the silver layer closest to the outer substrate carryingthe stack having a thickness slightly exceeding that of the secondsilver layer.

[0007] The laminated glazings according to said application are used aswindscreens, which explains why they have very high light transmissionvalues T_(L) of approximately 75%, in order to meet the safety standardsin force and therefore have a relatively high solar factor value SF. (Itis pointed out that the solar factor of a glazing is the ratio betweenthe total energy entering the room through said glazing and the incidentsolar energy).

[0008] The object of the invention is to develop a transparent substratecarrying a stack of thin layers having two layers which reflectradiation in the infrared and which are more particularly of a metallictype, so that they have a high selectivity, i.e. the highest possibleT_(L)/SF ratio for a given value of T_(L), while ensuring that saidsubstrate has an aesthetically satisfactory visual appearance inreflection.

SUMMARY OF THE INVENTION

[0009] Accordingly one object of the invention is to provide atransparent substrate, particularly of glass and having multiple thinlayers, on which are successively deposited a first dielectric materiallayer, a first layer having infrared reflection properties and inparticular based on metal, a second dielectric material layer, a secondlayer having infrared reflection properties, particularly based onmetal, and finally a third dielectric material layer. According to theinvention, the thickness of the first layer having infrared reflectionproperties, i.e. that closest to the carrying substrate, corresponds toabout 50-80%, particularly 55 to 75% and preferably 60-70% of thethickness of the second layer having infrared reflection properties. Anadvantageous example corresponds to a thickness of the first layercorresponding to about 65% of the second.

[0010] This great asymmetry in the thicknesses of the layers havinginfrared reflection properties makes it possible to advantageouslymodify the values of T_(L) and SF so as to obtain glazings having a goodselectivity, i.e. a good compromise between the need for transparencyand that of providing an optimum protection against solar heat rays.

[0011] Moreover, the choice of such an asymmetry leads to anotheradvantageous consequence. Not only does it make it possible to obtainglazings having an attractive visual appearance, particularly inreflection, i.e. having a neutral “whitewashed” coloring, but the visualappearance remains virtually unchanged regardless of the angle ofincidence with which the glazing is observed. This means that anexternal viewer of the facade of a building, entirely equipped with suchglazings, does not have a visual impression of a change of shade as afunction of the location on the facade at which he is looking. Thischaracteristic of appearance in uniformity is very interesting, becauseit is presently highly desired by building architects.

[0012] Moreover, the visual appearance of the glazing, both inreflection and transmission, can also be refined and controlled by anadequate selection of the materials and the relative thicknesses of thethree dielectric material layers.

[0013] Thus, according to a non-limiting first embodiment of theinvention, the optical thickness of the first dielectric material layeris chosen to be about equal to that of the third dielectric materiallayer. About equal optical thicknesses is to mean within 10%, preferablywithin 5%, more preferably within 2.5% of the thickness of the otherlayer. The optical thickness of the second dielectric material layer isthen advantageously chosen above or equal to 110% of the sum of theoptical thicknesses of the two other dielectric material layers (i.e.the first and third layers) and preferably corresponding to about 110 to120% of said sum.

[0014] In a second embodiment relating to the relative thicknesses ofthe dielectric material layers, which is advantageous, consists ofchoosing an optical thickness of the first dielectric material layerwhich exceeds the optical thickness of the third dielectric materiallayer. Thus, the optical thickness of the first dielectric materiallayer can correspond to at least 110% of the optical thickness of thethird dielectric material layer, particularly at least 110 to 140%,especially 115 to 135% and preferably about 125% of the opticalthickness of the latter. In the case of the drawing, it is recommendedthat the optical thickness of the second dielectric material layer bechosen to be about equal to the sum of the optical thicknesses of thetwo other dielectric material layers. About equal optical thicknesses isto mean within 10%, preferably within 5%, more preferably within 2.5% ofthe thickness of the other layer.

[0015] In the first and second embodiments cases, such relativeproportions between the optical thicknesses of the dielectric materiallayers makes it possible to obtain colors in reflection and even also intransmission, which are aesthetically appreciated and in particular blueand green.

[0016] However, the second embodiment has an additional advantagecompared with the first embodiment, to the extent that it optimizes the“non-sensitivity” of the complete stack to thickness variations of thedifferent dielectric material layers forming it. This means that slightthickness variations of one of the dielectric material layers in thestack does not lead to flagrant appearance deficiencies betweenindividual glazings or on the surface of the same glazing. This is veryimportant from the industrial standpoint, where manufacture takes placeof glazings having a considerable size and/or in large numbers with theaim of retaining appearances and performance characteristics which areas uniform as possible between individual glazing batches, particularlywithin individual zones of the same glazing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A more complete appreciation of the invention and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

[0018]FIG. 1 displays the positional relationship of a transparentsubstrate according the present invention, where the relativethicknesses of the layers is not indicated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] In terms of choice of material for said thin layer stack, it ispreferred to place on each of the layers having infrared reflectionproperties and in particular those layers based on metal, a thin“barrier” layer, particularly when the dielectric layer above the layerhaving infrared reflection properties is deposited by reactive cathodicsputtering in the presence of oxygen. Therefore said barrier layersprotect the metal layers in contact with the oxygen and themselvespartly oxidize during the deposition of the upper dielectric layer.Suitable “barrier layers” are preferably based on a tantalum, titaniumor nickel-chromium alloy and have a thickness of 1 to 3 nanometers.

[0020] With regards to the layers having infrared reflection properties,good results are obtained with silver layers.

[0021] The dielectric material layers are preferably based on tantalum(V) oxide, zinc oxide, tin (IV) oxide, niobium (V) oxide, titanium (IV)oxide or a mixture of certain of these oxides. It is also possible forone of the layers to be constituted by two superimposed oxide sublayers,one being of tin (IV) oxide and the other of an oxide making it possibleto improve the wetting of the layers having infrared reflectionproperties, such as tantalum (V) oxide or niobium (V) oxide inaccordance with French patent application 93/01546 filed on Feb. 11,1993 and European patent application 94 400 289.8 filed on Feb. 10,1994, or titanium (IV) oxide.

[0022] Each of the oxides given above has advantages. Thus, tin (IV)oxide and zinc oxide have high deposition speeds when deposited byreactive cathodic sputtering, which is of great interest industrially.However, tantalum (V) oxide or niobium (V) oxide make it possible toobtain an increased durability of the tack with respect to mechanical orchemical aggressions and in particular lead to a better wetting of thesilver layers when they are positioned below the latter. Mixed oxidescan offer a compromise between the deposition rate and the durabilityand the superimposing of two oxide layers reconciles in an optimummanner the cost of the starting materials and a wettability of thesilver layers.

[0023] There is also an additional advantage associated with the use oftantalum (V) oxide. A glazing provided with a stack having such adielectric material can be blue both in reflection and in transmission,which is appreciated from the aesthetic standpoint and is alsosurprising, because usually, in transmission, the color obtained iscomplimentary of that obtained in reflection, when the thin layers inquestion are only slightly or non-absorbent.

[0024] A suitable substrate material is preferably a conventionaltransparent glass substrate used in optical applications, particularlysuch as automotive window glass and building window glass.

[0025] A preferred embodiment of the stack according to the inventionconsists of choosing a thickness of 7 to 9 nanometers for the firstmetal layer and a thickness of 11 to 13 nanometers for the second.Preferably the optical thickness of the first and third dielectricmaterial layers is between 60 and 90 nanometers, their geometricalthickness being in particular between 30 and 45 nanometers. The opticalthickness of the second layer is between 140 and 170 nanometers, whileits geometrical thickness is between 70 and 80 nanometers. It is pointedout that the optical thickness, as it refers to the dielectric materiallayers, is defined in a conventional manner by the product of the realgeometrical thickness of the dielectric material layer and therefractive index of the dielectric material forming it. As a function ofthe envisaged oxide type, the index varies between 1.9 and 2.1 for tin(IV) oxide or tantalum (V) oxide and to about 2.3 for oxides of theniobium (V) oxide type.

[0026] The transparent substrate coated with the stack according to theinvention can advantageously be incorporated into a multiple glazing andin particular as one of the glass layers of an insulating doubleglazing. In the latter case, the double glazing has a light transmissionvalue (T_(L)) between 60 and 70% and a solar factor SF of 0.32 to 0.42,which make it completely suitable for use in buildings. Moreover, itpreferably has in reflection, a virtually unchanged visual appearance,no matter what the vision incidence angle, the values of a*, b* in thecolorimetry system (L, a*, b*, c*) remaining unchanged, below 3 andnegative.

[0027] It can also form part of a laminated glazing with, in particular,a light transmission of about 70%.

[0028] Other features of the invention will become apparent in thecourse of the following descriptions of the exemplary embodiments whichare given for illustration of the invention and are not intended to belimiting thereof.

[0029] In all the examples, the successive deposits of the layers of thestack was performed by magnetic field-assisted cathodic sputtering,however, any other deposition procedure can be practiced provided thatit permits a good control and monitoring of the thicknesses of thelayers to be deposited.

[0030] The substrates on which the stacks are deposited were 4 mm thicksoda-lime-silica glass substrates, except for Examples 7 to 10, wherethe substrates were 6 mm thick. In double glazings, they were assembledwith another substrate identical to the first, but in the blank state,by means of a 10 mm space of gas, except for the Examples 7 to 8, wherethere was a 12 mm space of gas.

[0031]FIG. 1 shows the stack according to the invention and does notrespect proportions with respect to the thicknesses of the layers so asto facilitate understanding. It is possible to see the previouslydefined substrate 1, surmounted by a first tin (IV) oxide or tantalum(V) oxide dielectric material layer 2, a first silver infraredreflective layer 3, a titanium or Ni—Cr alloy barrier alloy (partlyoxidized) 4, a second tin (IV) or tantalum (V) oxide dielectric materiallayer 5, a second silver infrared reflective layer 6, another barrieralloy layer 7 identical to the first barrier alloy layer 4 and finally alast dielectric material layer 8 of one of the same oxides.

[0032] A suitable deposition apparatus comprises at least one sputteringchamber equipped with cathodes having targets made from appropriatematerials under which the substrate 1 successively passes. Suitabledeposition conditions for each of the layers are as follows:

[0033] The silver-based layers 3, 6 may be deposited with the aid of asilver target, under a pressure of 0.8 Pa in an argon atmosphere, thelayers 2, 5 and 8, when based on SnO₂, may be deposited by reactivesputtering with the aid of a tin target under a pressure of 0.8 Pa andin an argon/oxygen atmosphere, including 36 vol.% oxygen.

[0034] The layers 2, 5, 8, when based on Ta₂O₅ or Nb₂O₅ may be depositedby reactive sputtering respectively with the aid of a tantalum target ora niobium target under a pressure of 0.8 Pa and in an argon/oxygenatmosphere, whereof about 10 vol.% is oxygen.

[0035] The layers 4, 7 based on Ni—Cr or titanium may be deposited withthe aid of a nickel-chromium alloy or titanium target under the samepressure and in an argon atmosphere.

[0036] The power densities and travel speeds of the substrate 1 may beadjusted in a known manner so as to obtain the desired layerthicknesses.

[0037] In all the following Examples, with the exception of the last,tantalum (V) oxide is chosen as the dielectric material for the layers2, 5 and 8.

EXAMPLES 1 TO 5

[0038] Examples 1, 2 and 5 are comparative examples to the extent thatin these three-cases, the silver layers 3 and 6 have either virtuallyidentical thicknesses (Example 1) or different thicknesses, but wherethe asymmetry is reversed compared with that of the invention (Examples2 and 5). Examples 3 and 4 are in accordance with the teachings of thepresent invention.

[0039] The following Table 1 gives for each of the Examples the natureand thicknesses (in nanometers) of the layers of the stack in question.The barrier layers 4 and 7 are designated Ni—Cr, knowing that they arein fact partly oxidized once all the layers have been deposited. TABLE 1Ex. 1 Ex. 2 Ex. 3 Ex. 4 5 Glass (1) — — — — — Ta₂O₅ (2) 36.5 34.5 32 3232 Ag (3) 10 11.5 8 8 12 Ni—Cr (4) 2 2 2 3 2 Ta₂O₅ (5) 77.5 94.5 77.572.5 77.5 Ag (6) 11 8 12 12.5 8 Ni—Cr (7) 2 2 2 2 2 Ta₂O₅ (8) 33.5 3533.5 32 33.5

[0040] The following Table 2 indicates for each of the above Examplesthe light transmission value T_(L) as a percentage, the solar factor SFcalculated according to DIN standard 67507 (Appendix A 233) as apercentage, the dominant wavelength values lambda-dom-t nanometers andthe associated coloring purity (p.t.) as a percentage. Also indicatedare the light reflection values R_(L) as a percentage, the dominantwavelength in reflection lambda-dom-r and the reflection purity (p.r.)as a percentage, the colorimetry measurements having been performedunder normal incidence. All the measurements relate to the substratefitted as a double glazing, with reference to the illuminant D₆₅. TABLE2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 T_(L) 69 66 70 61 62 SF 42 42 42 38 38Lambda-dom-t 493 489 498 490 478 p.t. 2 5 2 4 6 R_(L) 12 19 10 10 21Lambda-dom-r 561 641 486 487 574 p.r. 3 9 3 6 35

[0041] The following Table 3 gives the values of the dominant wavelengthin reflection lambda-dom-r, the reflection purity p.r. for some of thepreceding examples (the substrate still being installed in a doubleglazing), but on this occasion measured with an angle of incidentrelative to the perpendicular to the plane of the substrate ofrespectively 60 and 70°. TABLE 3 Ex. 1 Ex. 2 Ex. 3 Ex. 5 Lambda-dom-r(60°) 470 569 480 571 p.r. (60°) 5.4 3 4.68 8 R_(L) (60°) 19 28 20 27Lambda-dom-r (70°) 462 490 481 −498 p.r. (70°) 4.3 4 3.0 0.8 R_(L) (70°)32 39 34 36

[0042] Other colorimetry measurements with incidence angles 0° and 60°were performed, on this occasion in the system (L*, a*, b*), forExamples 2 and 3, as well as for example 5, which is in all pointsidentical to example 3, except that the silver layers 3 and 6 werereversed and consequently falling outside the conditions recommended bythe invention. Table 4 groups the values of a* and b*, as well as c*called saturation and equal to the square root of the sum of the squaresof a* and b*. TABLE 4 Ex. 2 Ex. 3 Ex. 5 a* (0°) 12.2 −0.9 −2.2 b* (0°)3.1 −3.1 22 c* (0°) 12.6 3.2 22.1 a* (60°) −1 −0.9 −1.7 b* (60°) 2 −3 6c* (60°) 2.2 3.13 6.2

[0043] The following conclusions can be drawn from this information.

[0044] Under a normal incidence angle, i.e., giving differentthicknesses to the silver layers and solely in such a way that thesilver layer closest to the substrate is much thinner, enables theobtaining of glazings which are blue in reflection.

[0045] It should be noted that the glazings according to the invention,particularly when the chosen dielectric is tantalum (V) oxide, are alsoblue in transmission.

[0046] Thus, only Examples 3 and 4 have lambda-dom-r values ofapproximately 486 nanometers and lambda-dom-t values of 490 nanometers,according to Table 2. However, the glazings of Examples 1 and 5 have inreflection a yellow shade, whereas that of Example 2 is a red-purpleshade.

[0047] In addition, the coloring purity in reflection p.r. of Example 2,close to 10%, is much higher than that of Examples 3 and 4 according tothe invention. (This value of p.r. is even higher for Example 5).

[0048] Moreover, the glazings of Examples 3 and 4 according to theinvention have a good selectivity of at least 1.6 or 1.7 with a solarfactor remaining equal to or below 42%.

[0049] Thus, the obtaining of a favorable colorimetry according to theinvention is not to the detriment of the solar protection performancecharacteristics of the glazings in question.

[0050] Tables 3 and 4 make it possible to evaluate the uniformity of theappearance in reflection of the glazings according to certain of thepreceding examples. Table 3 shows that the glazing according to Example3 in accordance with the invention retains a blue color in reflection,with a lambda-dom-r value remaining virtually constant towards 486 at 0°to 481 at 70°, the purity in reflection also remaining very moderate.

[0051] However, the glazing according to Example 1, where the silverlayers approximately have the same thickness, passes from a yellow colorin reflection under normal incidence to a blue and then violet color at60° and then 70°.

[0052] Table 4 confirms that only Example 3 according to the inventionmakes it possible to maintain an identical colored appearance inreflection no matter what the incidence angle, because the values of a*and b* remain virtually unchanged, as does the saturation c*.

[0053] This is not the case with the glazings of Examples 2 and 5, wherethe values of a* and b* change completely as a function of the incidenceangle. Thus, the value of a* passes, for the glazing of Example 2, froma very high positive value of 12.2 at 0° to a very low negative value of−1 at 60°.

[0054] Thus, only the examples according to the invention reconcile theselectivity and appearance uniformity.

EXAMPLES 6 AND 7

[0055] These two examples use as the dielectric material tin (IV) oxideand not tantalum (V) oxide and use for the barrier layers eithertitanium (Example 6) or Ni—Cr (Example 7).

[0056] The following Table 5 indicates the thickness values innanometers used for each of the stack layers: TABLE 5 Ex. 6 Ex. 7 Glass(1) — — SnO₂ (2) 34 32 Ag (3) 8 8 Ti or Ni—Cr (4) 1 1.5 SnO₂ (5) 77 74.5Ag (6) 12 11.6 Ti or Ni—Cr (7) 1 1.5 SnO₂ (8) 35 33

[0057] The thus coated substrates were installed in double glazings, asexplained hereinbefore. The photometric measurements on the doubleglazings appear in Table 6 (measurements under normal incidence). TABLE6 Ex. 6 Ex. 7 T_(L) 66 65 SF 38 39 R_(L) 10.4 9.4 lambda-dom-r 511 484p.r 2 2 a* — −0.5 b* — −1.1

[0058] These glazings, like those of Examples 3 and 4, reveal nosignificant modification of their visual appearance in reflection, nomatter what the measurement angle. In reflection they have a colortowards the greens for Example 6 and towards the blues for Example 7,but these colors remain very neutral, in view of the very low purityvalues associated therewith.

[0059] Laminated glazings incorporating the covered substrates of thestack according to the invention retain the favorable colorimetryobserved in the case of monolithic substrates or substrates installed indouble glazings.

[0060] Thus, the substrate covered with the stack according to Example 3was assembled with another substrate of the same type, but without alayer, using standard, 0.3 mm thick, polyvinyl butyral film.

[0061] The following Table 7 give for said laminated glazing the alreadyexplained values of T_(L), p.t. lambda-don-t, a* and b* in connectionwith the appearance in transmission, as well as the corresponding valuesR_(L), p.r. lambda-don-r, a* and b* concerning the appearance inreflection on the side of the substrate provided with the stack oflayers (same units as hereinbefore). TABLE 7 T_(L) 70 p.t. 1.2lambda-dom-t 502 a* −3.27 b* 0.52 R_(L) 14 p.r. 8 lambda-dom-r 483 a*−2.2 b* −4.4

[0062] Table 7 shows that the incorporation of substrates covered inaccordance with the invention in a laminated glazing structure leads tono deterioration of their aesthetic colorimetry. The thus obtainedlaminated glazing remains in the blues or greens, both in transmissionand in reflection.

[0063] Examples 3, 4 and 6 according to the invention relate to its“first variant” mentioned hereinbefore, i.e., respecting a choice ofrelative thicknesses between the three oxide layers 2, 5 and 8 which isspecific and approximately as follows. The thickness of the layer 2 isapproximately as follows. The thickness of the layer 2 is approximatelyequal to that of the layer 8 and the thickness of the layer 5 (in thecenter) is slightly greater than the sum of the thicknesses of the twoother layers 2 and 8 (in these examples reference can be made to eitherthe geometrical thickness or the optical thickness, because the threelayers are made from the same oxide).

[0064] The “second variant” according to the invention will now beillustrated by the following example and more particularly Example 8. Inthis variant, the thickness ratios between the oxide layers 2, 5 and 8are slightly modified, the optical thickness of the layer 2 beingsignificantly (25%) higher than that of the layer 8. The opticalthickness of the layer 5 (or the sum of the optical thicknesses of thedifferent sublayers forming it) is here approximately equal to the sumof the optical thicknesses of the two other layers 2 and 8.

EXAMPLE 8

[0065] The substrate according to Example 8 is covered with a stacksimilar to that described for Example 7, the layers 2, 5 and 8 being oftin (IV) oxide, but of different thicknesses.

[0066] The following Table 8 gives the thickness values in nanometers ofall the layers of the stack in question. TABLE 8 Ex. 8 Glass (1) — SnO₂(2) 41 Ag (3) 8 Ni—Cr (4) 1.5 SnO₂ (5) 74.5 Ag (6) 12 Ni—Cr (7) 1.5 SnO₂(8) 33

[0067] The substrate is fitted in a double glazing. The photometricmeasurements performed on the double glazing are given in table 9(measured under normal incidence). TABLE 9 Ex. 8 T_(L) 65 SF 39 R_(L)9.1 Lambda-dom-r 486 p.r. 1 a* −0.7 b* −0.5

[0068] Comparing these results with those obtained in Example 7, it canbe seen that identical values of T_(L) and SF are obtained. Theappearance in reflection is also in the blues, with an even more neutralcolor, because the purity is approximately 1% and the values of a* andb* are both well below 1. Another advantage of the stack type accordingto Example 7 is that it more easily permits slight thickness variationsin the stack layers, from one point to the other of the substrate,without giving rise to noticeable modifications of its visualappearance.

[0069] Thus, on performing measurements of a* and b* in reflection atdifferent points of the substrate according to Example 8 fitted in adouble glazing, it is found that the value differences remain below 1,i.e. differences which cannot be noticed by the human eye, even if eachof the layers has local thickness variations of +/−4%. This is veryimportant from the industrial standpoint, because it makes it moreeasily possible to obtain glazings which are both uniform, i.e. havingno local appearance modifications, and reproducible, i.e. having anidentical appearance between individual glazings or between individualglazing batches. This means that for a given production line, which hasits own performance limits, particularly with regards to the regularityof the layers obtained, such a stack will be less “sensitive” thanothers to thickness variations of the layers imposed by the line andwill consequently have a better optical quality.

[0070] Conversely, on imposing a given optical quality, it is possiblewith this type of stack, to use a production line under less draconianconditions or to use a production line having slightly inferiorperformance characteristics.

[0071] It is also advantageous from the industrial standpoint for thelayer 5 to have a thickness roughly equal to the sum of the thicknessesof the layers 2 and 8. Thus, it is then sufficient to use two targets,here of tin, whereof it is possible to regulate the power valuessupplied “once and for all” in their respective deposition chambers. Thelayer 2 is then obtained by the passage of the substrate under one ofthe targets with settings permitting the deposition of a predefinedadequate thickness. In the same way, the layer 8 is obtained by thepassage of the substrate under the second target with settings make itpossible to obtain the deposition of a previously defined adequatethickness. The layer 5 is obtained by consecutive passages of thesubstrate under each of the targets, so that on the substrate aresuperimposed a layer thickness corresponding to that of the layer 2 or 8and then a layer thickness corresponding to that of the layer 8 or 2,i.e. the sum of the thicknesses of these two layers is formed withoutcalling on a third target.

EXAMPLES 9 TO 12

[0072] The aim of these examples is to optimize the wettability andtherefore the performance characteristics of at least one of the silverlayers. They follow the teaching of European patent application 94 400289.8.

[0073] In the case of Examples 9 and 10, the layers 2 and 8 are onceagain of tin (IV) oxide, but the layer 5 is subdivided into twosuperimposed bislayers, the first 5 being of tin (IV) oxide and thesecond 5 bis of tantalum (V) oxide (for Example 9) or niobium (V) oxide(for Example 10). A thin metallic sublayer can be optionally providedbelow the silver layer 6 and which is of NiCr or Sn.

[0074] In the case of Examples 11 and 12, the layer 2 is also subdividedinto two superimposed sublayers, the first 2 being of tin (IV) oxide andthe second 2 bis of tantalum (V) oxide (for Example 11) or niobium (V)oxide (for Example 12). An optional, thin metallic sublayer can beprovided beneath the silver layer 3.

[0075] Thus, in the case of Examples 9 and 10, the wettability of thesecond silver layer 6 is optimized, whereas in the case of Examples 11and 12, the wettability of the two silver layers 3 and 6 is optimized.

[0076] Table 10 gives the thicknesses in nanometers of the layerspresent. TABLE 10 Ex. 9 and 10 Ex. 11 and 12 Glass (1) — — SnO₂ (2) 4130 − 31 Ta₂O₅ or Nb₂O₅ (2 bis) 0 10 Ag (3) 8 8 Ni—Cr (4) 1.5 1.5 SnO₂(5) 64 64 Ta₂O₅ or Nb₂O₅ (5 bis) 10 10 Ag (6) 12 12 Ni—Cr (7) 1.5 1.5SnO₂ (8) 33 33

[0077] There is a slight improvement to the solar control performancecharacteristics of the stacks. Moreover, the use of oxides known fortheir hardness, such as tantalum or niobium (V) oxide, helps to optimizethe durability of the overall stack and in particular its mechanicaldurability. This mechanical strength increase is particularly pronouncedfor Examples 11 and 12.

[0078] In conclusion, the glazings according to the invention have botha good selectivity of about 1.70, a uniform visual appearance which isattractive to the eye (particularly a blue or green color in reflectionand optionally also in transmission), as well as a range of lighttransmission values making them suitable for use as solar controlglazings in buildings, particularly in the form of double glazings, thestack of thin layers preferably being on face 2 (the faces areconventionally numbered from the outside to the inside of the room inquestion).

[0079] The substrates covered with layers according to the invention canalso be used with advantage for producing laminated glazings.

[0080] Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

[0081] This application is based on French patent applications FR93/09917 filed in France on Aug. 12, 1993 and FR 94/02723 filed inFrance on Mar. 9, 1994, the entire contents of which of each are herebyincorporated by reference.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A transparent substrate having multiple thinlayers comprising successively: i) a first dielectric material layer;ii) a first layer having infrared reflection properties; iii) a seconddielectric material layer; iv) a second layer having infrared reflectionproperties; v) a third dielectric material layer, wherein a thickness ofsaid first layer having infrared reflection properties is 50 to 80% ofthat of said second layer having infrared reflection properties.
 2. Thetransparent substrate of claim 1 , wherein the optical thickness of saidsecond dielectric material layer is equal to or greater than 110% of thesum of the optical thicknesses of said first and third dielectricmaterial layers.
 3. The transparent substrate of claim 2 , wherein theoptical thicknesses of said first dielectric material layer and saidthird dielectric material layer are about equal.
 4. The transparentsubstrate of claim 1 , wherein the optical thickness of said firstdielectric material layer is greater than the optical thickness of saidthird dielectric material layer; and wherein the optical thickness ofsaid first layer corresponds to at least 110% of the optical thicknessof said third layer.
 5. The transparent substrate of claim 4 , whereinthe optical thickness of said second dielectric material layer is aboutequal to the sum of the optical thicknesses of said first and thirddielectric layers.
 6. The transparent substrate of any one of claims 1to 5 , wherein each of said layers having infrared reflection propertiesis surmounted by a thin, partly oxidized, barrier metal layer.
 7. Thetransparent substrate of any one of claims 1 to 5 , wherein each of saidlayers having infrared reflection properties are based on silver.
 8. Thetransparent substrate of any one of claims 1 to 5 , wherein at least oneof said three dielectric material layers is a material selected from thegroup consisting of tantalum (V) oxide, tin (IV) oxide, zinc oxide,niobium (V) oxide, titanium (IV) oxide or mixtures of said oxides, or isconstituted by oxide or mixtures of said oxides, or is constituted by afirst tin (IV) oxide layer surmounted by a second layer of tantalum (V)oxide, niobium (V) oxide or titanium (IV) oxide.
 9. The transparentsubstrate of any one of claims 1 to 5 , wherein the thickness of saidfirst layer having infrared reflection properties is between 7 and 9nanometers.
 10. The transparent substrate of any one of claims 1 to 5 ,wherein the thickness of said second layer having infrared reflectionproperties is between 11 and 13 nanometers.
 11. The transparentsubstrate of any one of claims 1 to 5 , wherein the optical thickness ofsaid first and third dielectric material layers is between 60 and 90nanometers; and wherein the optical thickness of said second dielectricmaterial layer is between 140 and 170 nanometers.
 12. The transparentsubstrate of claim 1 wherein the thickness of said first layer havinginfrared reflection properties is 55 to 75% of that of said second layerhaving infrared reflection properties.
 13. The transparent substrate ofclaim 1 wherein a thickness of said first layer having infraredreflection properties is 60 to 70% of that of said second layer havinginfrared reflection properties.
 14. The transparent substrate of claim 1, wherein the optical thickness of said second dielectric material layeris between about 110% to 120% of the sum of the optical thicknesses ofsaid first and third dielectric material layers.
 15. The transparentsubstrate of claim 1 , wherein the optical thickness of said firstdielectric material layer corresponds to at least 110% to 140% of theoptical thickness of said third dielectric material layer.
 16. Thetransparent substrate of claim 1 , wherein the optical thickness of saidfirst dielectric material layer corresponds to about 125% of the opticalthickness of said third dielectric material layer.
 17. The transparentsubstrate of claim 6 , wherein said barrier metal layer is based on amaterial selected from the group consisting of titanium andnickel-chromium alloy.
 18. The transparent substrate of claim 6 ,wherein said barrier metal layer has a thickness of from 1 to 3nanometers.
 19. A laminated glazing comprising the transparent substrateof any one of claims 1 to 5 , wherein said laminated glazing has a lighttransmission T_(L) of about 70% and a color in external reflection inthe blues or greens.
 20. A multiple glazing comprising the transparentsubstrate according of any one of claims 1 to 5 , wherein said multipleglazing has a light transmission (T_(L)) between 60 and 70% and a solarfactor of 0.32 to 0.42.
 21. The multiple glazing of claim 20 , whereinsaid multiple glazing is a double glazing.
 22. A multiple glazingcomprising the transparent substrate according of any one of claims 1 to5 , wherein said multiple glazing has a color in external reflection inthe blues.
 23. The multiple glazing of claim 22 , wherein said multipleglazing has a color in external transmission in the blues.
 24. Themultiple glazing of claim 22 , wherein said dielectric material layersare tantalum (V) oxide.
 25. The multiple glazing of claim 22 , whereinsaid multiple glazing is a double glazing.
 26. The multiple glazingaccording to claim 22 , wherein said multiple glazing has an opticalappearance in external reflection which remains virtually identical nomatter what the incidence angle, the values of a* and b* in thecolorimetry system remaining unchanged and below 3 and having a negativesign.